Understanding the circulation in the deep, micro-tidal and strongly stratified Congo River estuary

2021 ◽  
pp. 101890
Author(s):  
Valentin Vallaeys ◽  
Jonathan Lambrechts ◽  
Philippe Delandmeter ◽  
Johannes Pätsch ◽  
Alejandro Spitzy ◽  
...  
Keyword(s):  
River Estuary ◽  
Congo River

Geochemistry of the Congo River, estuary, and plume

2013 ◽  
pp. 554-583 ◽  
Author(s):  
R. G. M. Spencer ◽  
A. Stubbins ◽  
J. Gaillardet
Keyword(s):  
River Estuary ◽  
Congo River

Carbon and oxygen budget in the deep, strongly stratified Congo River Estuary

2020 ◽  
Author(s):  
Valentin Valleys ◽  
Johannes Pätsch ◽  
Jonathan Lambrechts ◽  
Philippe Delandmeter ◽  
Emmanuel Hanert ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Water Body ◽  
River Estuary ◽  
In Situ Observation ◽  
Oxygen Balance ◽  
Exchange Flow ◽  
Oceanic Water ◽  
Congo River ◽  
Poc Flux ◽  
River Region

<p>The Congo River region of freshwater influence (ROFI) is characterized by a deep canyon that connects the river to the deep ocean by cutting through the continental shelf (Shepard & Emery, 1973). In the estuary, high discharge of freshwater and very small vertical mixing within the canyon restricts the supply of oxygen from the surface waters to the more saline bottom waters, where the remineralisation of riverine particulate organic carbon leads to hypoxia (Eisma & Van Bennekom, 1978). We study the dynamics of the Congo River ROFI by applying the multi-scale baroclinic coastal ocean model SLIM 3D (www.slim-ocean.be) to this challenging environment. Model results compare favourably against in-situ observation in the estuary, suggesting that the exchange flow is correctly simulated. Using water ages as a diagnostic tool allows gaining deeper insight into the fate of riverine and oceanic water.</p><p>We use the simulated renewing time of the canyon’s water body by oceanic water (R = 20 d) to calculate an oxygen and carbon budget of the subhalocline water body from the remineralization of POC.</p><p>The renewing oceanic waters originate from the Eastern Atlantic equatorial oxygen minimum zone.  At a representative station in the canyon 60 km offshore the oxygen concentration was measured as 0,05 – 0,1 [mol O<sub>2</sub>/m3] at water depths of 200 - 500 [m]. Following Eisma & Kalf (1984) we split the recent Congo River POC flux of 5260 [mol C s<sup>-1</sup>] (Coynel et al., 2005) into 50 % settling into the subhalocline water body, the other 50 % being advected offshore with the surface plume. Given these assumptions for the oxygen and carbon boundary fluxes, only 15 % of the settling POC are remineralised by aerobic degradation within the canyon, confirming oxygen limitation and leaving a substantial fraction of available labile POC undegraded (generally 35 % of tropical riverine POC are labile; Ittekkot, 1988). Summing up, the canyon’s oxygen balance is ocean oxygen- rather than river POC - controlled, and scenarios of even substantial future POC-flux reductions by land use change and/or reservoir construction within the catchment should therefore not imply significant changes in the Congo River estuarie’s oxygen balance.</p><p>Coynel, A., P. Seyler, H. Etcheber, M. Meybeck  &  D. Orange (2005) Spatial and seasonal dynamics of total and suspended sediment and organic carbon species in the Congo River. Global Biogeochemical Cycles, <strong>19</strong>,GB4019, doi: 10.1029/2004GB002335.</p><p>Eisma, D. & A.J. Van Bennekom (1978) The Zaire river and estuary and the Zaire outflow in the Atlantic Ocean. Netherlands J. Sea Res. <strong>12</strong> (3-4): 255-272.</p><p>Eisma, D. & J. Kalf (1984) Dispersal of Zaire river suspended matter in the estuary and  the Angola Basin. Netherlands J. Sea Res. <strong>17 </strong>(2-4): 385-411.</p><p>Ittekkot, V. (1988) Global trends in the nature of organic matter in river suspensions. Nature, <strong>332</strong>, 436-438.</p><p>Shepard, F.P. & K.O. Emery (1973) Congo submarine canyon and fan valley. Bull. Am. Assoc. Petrol. Geol. <strong>57</strong>: 1679-1691.</p>

Mineral phases and processes within green peloids from two Recent deposits near the Congo River Mouth

Clay Minerals ◽  
1988 ◽  
Vol 23 (4) ◽  
pp. 447-458 ◽  
Author(s):  
P. Giresse ◽  
A. Wiewiora ◽  
B. Lacka
Keyword(s):  
River Estuary ◽  
River Mouth ◽  
Octahedral Sheet ◽  
Rich Phase ◽  
Density Fractions ◽  
Congo River ◽  
Mineral Phases ◽  
Crystallochemical Formula ◽  
High Sedimentation ◽  
Recent Sediments

AbstractIn the Recent sediments of the Congo River estuary, the green Fe-bearing peloids containing 7 Å phases are nearer to the river mouth than the 10 Å phyllosilicates. Measurements of d060 for 7 Å minerals in various density fractions indicated a progressive transformation of kaolinite into trioctahedral 1:1 phyllosilicates in the zone with a high sedimentation rate. Projection of the chemical composition from the approximate crystallochemical formula on to a classification field confirmed the transformation of kaolinite into a 7 Å Fe-rich phase via substitution of Fe2+ and Mg for Al in the octahedral sheet, with insignificant changes in the tetrahedral sheet. The resultant transition phase has a composition closer to greenalite than berthierine. The possible advancement of the evolution process was stopped by massive formation of goethite. The 10 Å minerals formed in the grains deposited in the off-shore sediments have a homogenous composition and occur in association with goethite and quartz. These peloids show an enrichment in Al although no kaolinite is present.

Climate-associated trends and variability in ichthyoplankton phenology from the longest continuous larval fish time series on the east coast of the United States

2020 ◽  
Vol 650 ◽  
pp. 269-287
Author(s):  
WC Thaxton ◽  
JC Taylor ◽  
RG Asch
Keyword(s):  
United States ◽  
Environmental Variability ◽  
Larval Fish ◽  
Interspecific Interactions ◽  
River Estuary ◽  
Atlantic Multidecadal Oscillation ◽  
The United States ◽  
Larval Survival ◽  
Ecological Communities ◽  
Northerly Wind

As the effects of climate change become more pronounced, variation in the direction and magnitude of shifts in species occurrence in space and time may disrupt interspecific interactions in ecological communities. In this study, we examined how the fall and winter ichthyoplankton community in the Newport River Estuary located inshore of Pamlico Sound in the southeastern United States has responded to environmental variability over the last 27 yr. We relate the timing of estuarine ingress of 10 larval fish species to changes in sea surface temperature (SST), the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, wind strength and phenology, and tidal height. We also examined whether any species exhibited trends in ingress phenology over the last 3 decades. Species varied in the magnitude of their responses to all of the environmental variables studied, but most shared a common direction of change. SST and northerly wind strength had the largest impact on estuarine ingress phenology, with most species ingressing earlier during warm years and delaying ingress during years with strong northerly winds. As SST warms in the coming decades, the average date of ingress of some species (Atlantic croaker Micropogonias undulatus, summer flounder Paralichthys dentatus, pinfish Lagodon rhomboides) is projected to advance on the order of weeks to months, assuming temperatures do not exceed a threshold at which species can no longer respond through changes in phenology. These shifts in ingress could affect larval survival and growth since environmental conditions in the estuarine and pelagic nursery habitats of fishes also vary seasonally.

Động lực phát triển vùng cửa Sông Hậu (cửa Định An - Tranh Đề)

2008 ◽  
Vol 30 (2) ◽  
pp. 130-135
Author(s):  
Hoa Mạnh Hùng ◽  
Nguyễn Quang Thành ◽  
Phan Thị Thanh Hằng
Keyword(s):  
River Estuary ◽  
River Mouth

Evaluating the dynamics of the Hau River estuary (Dinh An - Tranh De river mouth)

Investigational Studies on Quantity of Salinity in Netravati River Estuary Sand-Coastal Karnataka

2018 ◽  
Vol 6 (6) ◽  
pp. 46
Author(s):  
Raveesha P ◽  
K. E. Prakash ◽  
B. T. Suresh Babu
Keyword(s):  
Brackish Water ◽  
Sea Water ◽  
Salt Water ◽  
Construction Material ◽  
Salt Content ◽  
River Estuary ◽  
Sand Sample ◽  
River Sand ◽  
Natural Aggregates

The salt water mixes with fresh water and forms brackish water. The brackish water contains some quantity of salt, but not equal to sea water. Salinity determines the geographic distribution of the number of marshes found in estuary. Hence salinity is a very important environmental factor in estuary system. Sand is one major natural aggregate, required in construction industry mainly for the manufacture of concrete. The availability of good river sand is reduced due to salinity. The quality of sand available from estuarine regions is adversely affected due to this reason. It is the responsibility of engineers to check the quality of sand and its strength parameters before using it for any construction purpose. Presence of salt content in natural aggregates or manufactured aggregates is the cause for corrosion in steel. In this study the amount of salinity present in estuary sand was determined. Three different methods were used to determine the salinity in different seasonal variations. The sand sample collected nearer to the sea was found to be high in salinity in all methods.  It can be concluded that care should be taken before we use estuary sand as a construction material due to the presence of salinity.

DIVERSITY OF FISH LARVAE AROUND THE ESTUARY OF THE BANYUASIN RIVER, SOUTH SUMATERA PROVINCE

2020 ◽  
Vol 6 (2) ◽  
Author(s):  
Moh. Rasyid Ridho ◽  
Enggar Patriono ◽  
Sarno Sarno ◽  
Sahira Wirda
Keyword(s):  
Initial Phase ◽  
Sampling Method ◽  
Environmental Changes ◽  
Negative Impact ◽  
Fish Larvae ◽  
River Estuary ◽  
Sampling Technique ◽  
Critical Phase ◽  
Morisita Index ◽  
Index Value

The initial phase of the fish life cycle is a critical phase associated with high mortality due to sensitivity to predators, food availability, and also environmental changes that occur in nature. Disruption of the initial stages of fish life has a negative impact on fish populations. Until now there has been no information about fish larvae around the Banyuasin River Estuary. Therefore, research is needed on the diversity of fish larvae around the Banyuasin River Estuary, South Sumatra Province. This research were used purposive sampling method, sampling technique in the form of Cruise Track Design with continuous parallel survey trajectory. Based on the results of the study found as many as 10 families consisting of 1483 individuals of fish larvae in March and 1013 individuals of fish larvae in May consisting of Engraulidae 1,601 individuals of fish larvae, Mungiloidei as many as 109 individuals, Leiognathidae 50 individuals, Chanidae 453 individuals, Scatophagidae 20 individuals , Belonidae 39 individuals, Gobioididae 5 individuals, Chandidae 183 individuals, Syngnatihidae 6 individuals, and Gobiidae 30 individuals fish larvae. The index value of fish larvae diversity is classified as medium category (March 1.02 and May 1.12), Morisita index shows the distribution pattern of fish larvae classified as a group (March 0-14.17 and May 2.43-10.40 ), and the evenness index value is in the medium category (March 0.437 and May 0.521).

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